The reaction of 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) in 50/50 (v/v) trifluoroethanol/water at 25 °C is first-order in the concentration of azide anion nucleophile. A carbon-13 NMR analysis of the products of the reactions of Me-1-[α–13C]OTs in 50/50 (v/v) trifluoroethanol/water at 25 °C shows the formation of Me-1-[β–13C]OH, Me-1-[β–13C]OCH2CF3 and Me-1-[β–13C]N3 from the trapping of a symmetrical 4-methylphenonium ion reaction intermediate Me-2+. The formation of Me-1-[α–13C]N3 by concerted bimolecular displacement of azide ion at Me-1-[α–13C]OTs (kN = 3.8 × 10−6 M−1 s−1) and of Me-1-[α–13C]OH and Me-1-[α–13C]OCH2CF3 by concerted bimolecular displacement of solvent (ksolv = 1.8 × 10−8 s−1) is also observed. An analysis of the rate and product data provides a value of kaz/ks = 32 M−1 for partitioning of Me-2+ between addition of azide ion and solvent that is nearly 3-fold smaller than kaz/ks = 83 M−1 reported in an earlier study on the partitioning of MeO-2+ [J. Org. Chem. 2011, 76, 9568]. This change is attributed to a decrease in nucleophile selectivity with increasing electrophile reactivity for the activation-limited addition of solvent and azide anion to X-2+. These data set a limit of 1/ks ≥ 10−7 s for the lifetime of Me-2+ in aqueous solution.
Althoughmany researchers have studied the local scour phenomenon around a spur dike experimentally and analytically, almost all the studies have been carried out for the steady flow state. This paper focused on a local scour around a spur dike during a surge pass and bed variations around the spur dike is investigated numerically by using a two dimensional numerical model with flux difference splitting technique under unstructured grid system. At first, the applicability of the employed numerical method was examined under the steady flow state. Secondly, rapidly varied flow such as surge flow condition was applied.The numerical results show good agreement with the experimental results.
This paper presents 2-dimensional flow characteristics in a pool type fishway by using the VOF method. The fishway with 5 pools is treated as an object of the study. Considering the flow pattern of a pool type fishway, the analytical region is divided into 3 parts, which are the upstream part, the middle part and the downstream part of the fishway. As a result, the proposed method is able to reproduce the flow in the pool type fishway with many pools. And it is also clarified that the down stream water level condition plays a very important roll to design the pool type fishway.
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